Chains such as Rent-a-Wheel and Rimco are seeing business boom. Many consumers pay double or triple the cost of buying and face aggressive repossession policies. When the tires on their Dodge Caravan had worn so thin that the steel belts were showing through, Don and Florence Cherry couldn't afford to buy a new set. So they decided to rent instead. The Rich Square, N.C., couple last September agreed to pay Rent-N-Roll $54.60 a month for 18 months in exchange for four basic Hankook tires. Over the life of the deal, that works out to $982, almost triple what the radials...